(1) Field of the Invention
The present invention relates to a liquid crystal polyester-containing liquid composition which contains a liquid crystal polyester, an organic solvent and a leveling agent, a method for producing a resin film from the liquid crystal polyester-containing liquid composition, and a method for producing a liquid crystal polyester-impregnated fiber sheet from a liquid crystal polyester-containing liquid composition.
(2) Description of Related Art
A liquid crystal polyester has become of major interest as an electronic substrate material since it exhibits excellent high frequency characteristics and low hygroscopicity. Particularly a solution composition containing a liquid crystal polyester including a structural unit derived from an aromatic amine derivative, and an organic solvent is capable of producing a liquid crystal polyester film having small anisotropy by flow-casting on a support and removing the solvent from the flow-cast product, and is therefore excellent as a material of a film for electronic components (see, for example, JP-A-2004-315678 or JP-A-2005-342980)
On the other hand, the liquid composition containing a resin optionally contains various additives such as a coupling agent, a leveling agent, a defoamer, an ultraviolet absorber and a flame retardant, a coloring pigment or the like. Among these additives, the leveling agent is added while expecting that a surface of a resin film formed from a resin-containing liquid composition or a surface of a fiber sheet obtained by impregnating with a resin-containing liquid composition are modified. Similar to the other resin-containing liquid compositions, general description such as addition of a leveling agent is disclosed in a liquid composition containing a liquid crystal polyester (see, for example, JP-A-2002-329422 or JP-A-2003-16846). However, there is no specific description with respect to a compound to be used as a leveling agent, the addition amount thereof, the obtained effects and the like.
In the production process of a liquid crystal polyester-impregnated fiber sheet or film obtained using a liquid composition composed of a conventional liquid crystal polyester and solvent, the solvent is removed by drying at a high temperature so as to increase productivity. However, there is a problem that surface appearance becomes worse due to a decrease in solution viscosity and rapid volatilization of the solvent in case of drying at a high temperature.